Overedging device for sewing machines

ABSTRACT

A lockstitch sewing machine is disclosed having a mechanism whereby overedge stitches may be formed in the work fabric being sewn. A thread guiding insert accommodated in the lockstitch loop taker bobbin case directs each needle thread loop through an apertured throat plate and about the edge of a fabric being stitched for penetration of the thread loop by the sewing machine needle on a subsequent needle reciprocation.

United States Patent [451 July 25,1972

Killinger et al.

[54] OVEREDGING DEVICE FOR SEWING MACHINES [72] lnvcntors: Karl l-I. Klllinger; Stanley J. Ketterer, both of Jamesburg, NJ.

[73] Assignee: The Singer Company, New York, NY. 22 Filed: April 23, 1971 [21] Appl. No.: 136,672

[52] U.S.Cl ..112/162, 112/168 1 l [58] FieldofSearch ..112/162, 168,16,65,177

[5 6] References Cited UNITED STATES PATENTS 1,197,305 9/1916 Plumley ..112/162 2,321,747 6/1943 Hickey ..112/162 2,849,976 9/1958 Sanseverinati.. 12/168 X 3,253,560 5/1966 Ketterer et al ..112/168 Primary Examiner-James R. Boler Attorney-Marshall J. Breen, Chester A. Williams, Jr. and Robert E, Smith [57] ABSTRACT 7 Claims, 4 Drawing Figures Patented July 25, 1972 3,678,871

. INVENTOR. Karl H. Klllmger, BY Stanley J.Keft erer i 5&1

ATTORNEY BACKGROUND OF THE INVENTION therefore, the alternatives of use of an expensive special purpose commercial overedge machine or the production of a seam which is not a true overedge stitch.

SUMMARY OF THE INVENTION It is an object of this invention to provide fittings which can be accommodated in a conventional household lockstitch sewing machine whereby true overedge stitches may be formed. This object is attained by the provision of a needle thread loop guiding device associated with the bobbin case which is held stationary in the lockstitch loop taker. The thread guiding device includes a thread guiding finger which projects upwardly through an aperture in the throat plate so as to direct needle thread loops which are being manipulated by the loop taker about the edge of a fabric panel being stitched and into the path of reciprocation of the needle.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view, as will hereinafter appear, this invention is illustrated in the accompanying drawings of a preferred embodiment in which;

FIG. I represents a perspective view of the sewing head of a sewing machine including a fragment of the work support thereof, with the present invention applied thereto,

FIG. 2 is an enlarged perspective view of the sewing machine work support of FIG. 1 with the throat plate slide plate and presser foot displaced therefrom so as to expose the sewing machine loop taker,

FIG. 3 is a perspective view taken from the rear of the presser foot with the throat plate broken away and illustrating the formation of a stitch as a needle thread loop is being directed onto the thread guiding finger, and

FIG. 4 is a perspective view similar to FIG. 3 but illustrating the formation of a stitch as the needle descends into the thread loop held at the extremity of the thread guiding finger.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. I, this invention may be used with a household sewing machine of conventional arrangement including a work supporting bed 11 with a bracket arm I2 extending over the work supporting bed and having a thread carrying needle 13 secured by a clamp 14 to a needle bar 15 endwise reciprocable in the sewing head. Also supported for limited vertical movement in the bracket arm is a presser bar 16 to which a presser foot 17 is secured by a clamp screw 18. The presser foot is preferably spring biased downwardly so as to hold work fabrics against a throat plate I9 which is fastened over an opening 20 in the work supporting bed as for instance, by retaining posts 21 one at each side of the bed opening 20. Theretaining posts may be slotted as at 22 with each slot accommodating a notched portion 23 formed on opposite sides of the throat plate securely to clamp the throat plate in place on the bed. The opening 20 in the work supporting bed is additionally closed by a slide plate 24 which may be retracted to expose a loop taker 25 which is carried in the bed within the opening 20. The loop taker 25 is of a type which cooperates with the needle 13 in the formation of lockstitches (Federal Stitch Type 301). The loop taker 25 illustrated in the drawings is of the type disclosed in greater detail in the US. Pat. No. 3,154,035, Oct. 27, 1967, W. J. Edwards et al to which reference may be had for a detailed description. For an understanding of the present invention, it will be sufiicient to keep in mind that the loop taker 25 includes a rotary basketshaped body 26 which is formed at the rim with the loop seizing beak 27. .lournalled in the rotary body 26 is a bobbin case 28 which is restrained against rotation by rotation restraining elements 29 and 30. The bobbin case 28 includes a downwardly biased latch arm 31 which spans a bobbin accommodating recess 32 in the bobbin case and ordinarily serves to restrain in place in the bobbin case a thread carrying bobbin (not shown) which is necessary for the formation of lockstitches. The above referenced US. Pat. No. 3,154,035 illustrates and describes in detail the manner in which the bobbin in conventionally accommodated in the above described loop taker bobbin case.

In the present invention a thread guiding device indicated generally at is accommodated in the bobbin case in place of a bobbin. The thread guiding device is illustrated apart from the loop taker 25 in FIGS. 3 and 4 and it is shown in place in the bobbin case of the loop taker in FIG. 2. The thread guiding device is preferably formed with a circular base plate 41 which is made substantially the same size as the top flange of a bobbin which is conventionally accommodated in the bobbin case. The base plate 4! is preferably formed with a central depression 42 for accommodating a locating protuberance 43 on the latch arm 31. The base plate is also formed with raised peripheral lugs 44 and 45 at each side of the latch arm 31 to prevent rotation and lend an increased measure of stability to the thread guiding device in the loop taker bobbin case. Secured as by rivets to the baseplate 41 is a flat support arm 51 from which is struck up a thread guiding finger 52. The support arm 5] is preferably formed with an inclined outer edge 53 to encourage thread loops being manipulated by the loop taker 25 to move freely thereon. The thread guiding finger 52 is shaped with a gradually tapering form which encourages each thread loop being manipulated by the loop taker to be drawn upwardly along the-thread guiding finger and toward a free extremity 54 thereof which, as illustrated in the drawings extends above the level of the work support I I of the sewing machineacross and in front of the path of needle reciprocation, and includes on the free extremity a rounded forwardly offset thread detaining projection 5.

As best shown in FIG. 2, the throatplate 19 is formed with conventional feed dog accommodating slots through which moves a conventional feed dog 61 by which work fabrics are transported across the sewing machine work support 11. The throat plate is also formed with a needle aperture 62 through which the needle 13 reciprocates in cooperation with the loop taker 25. Preferably the needle aperture 62 is formed as an extension of one of the feed dog slots 60. In order to accommodate the upwardly extending thread guiding finger 52 the throat plate laterally of the needle aperture 62 and of the feed dog slots 60 is formed with an opening 63 through which the thread guiding finger projects. The opening 63 communicates with one of the feed dog slots 60 and with the needle aperture 62 so that the threads which are manipulated upwardly through the opening 63 by the thread guiding finger 52 will not become knotted or caught on the throat plate. As shown in FIG. I, the throat plate opening 63 beneath the thread guiding finger 52 is formed with a thread camming edge 64 which traverses beneath the free extremity 54 of the thread guiding finger and serves to position needle thread loops on the free extremity of the thread guiding finger in such a position as shown in FIG. 4, that during a subsequent needle reciprocation the needle will penetrate the thread loop thereon.

To facilitate the fonnation of overedge stitches and to facilitate the movement of overedge stitches from the stitching point after they are formed, the presser foot 17 is preferably provided with a sole plate formed with a needle accommodating aperture 71 and formed at one side of the needle aperture with a thread loop supporting finger 72.

The operation of the present invention is best illustrated in FIGS. 3 and 4 in which the presser foot I7 and the thread guiding device 40 are illustrated viewed from the rear of the presser foot and shown with sewing thread in different positions during the formation of a stitch. In these figures a needle thread loop while influenced by the thread guiding finger 52 is indicated at L and when released from the finger and incorporated into the line of stitching is indicated at 3. As each successive needle thread loop is seized and manipulated by the loop seizing beak 27 of the sewing machine loop taker 25, it is directed onto the thread guiding finger 52 as shown at L in FIG. 3. As the thread is tightened in the process of setting the previously formed loop S, the thread loop L will be drawn outwardly along the thread guiding finger until it is detained at the free extremity 54 by the lateral projection 55. In this position, detained on the free extremity of the thread guiding finger as illustrated in FIG. 4, the thread camming edge 64 of the throat plate will influence the position of the loop L favorably for entry by the needle on the next penetration thereof. As the needle 13 penetrates the thread loop 11 a fresh loop of the needle thread is carried therethrough by the needle as shown in FIG. 4 and when this fresh needle thread loop is seized by the loop taker loop seizing beak 27 the downward v pull of this thread on the old loop L will influence the thread loop L to be shed from the free end 54 of the thread guiding finger 52 to form a stitch over the stitch supporting finger 72 of the presser foot. The stitches will, of course, be transported by the sewing machine feed dog off the free end of the stitch supporting finger 72.

In the preferred form of this invention described above a single thread chainstitch overedge stitch will be formed (Federal Stitch Type 501). This is the simplest form of overedge stitch and requires no additional operating mechanism for stitch formation other than that described above. The principles of this invention, and particularly the arrangement including a thread guiding finger 52 carried by a conventional lockstitch loop taker for directing successive loops of needle thread being manipulated by the loop taker above the level of the sewing machine work support and about the edge of a fabric being stitched may also find utility in more complicated types of stitching apparatus which are not shown or described herein, but which include mechanism for introducing and concatenating additional threads into the seam for forming multiple thread chainstitch overedge stitches as will be apparent to those skilled in the sewing art.

Having set forth the nature of this invention, what is claimed herein is:

I. An overedge chainstitch forming attachment for use on a lockstitch sewing machine of the type having a thread carrying needlereciprocable through a needle aperture in a work supporting throat plate in cooperation with a circularly moving loop taker which is arranged beneath the throat plate and includes a bobbin case restrained stationary therein, said overedge chainstitch forming attachment including a throat plate formed with an opening laterally opposite the needle aperture therein, a thread guiding device adapted to be secured in a stationary position on said bobbin case so as to be encompassed by each needle thread loop which is manipulated by said loop taker, and a thread guiding finger projecting from said thread guiding device upwardly through said throat plate opening when said thread guiding device is secured on said bobbin case successively to direct each needle thread loop being manipulated by said loop taker upwardly across the edge of a work fabric on the throat plate.

2. An overedge chainstitch forming attachment as set forth in claim 1 in which said thread guiding finger is formed with a free extremity extending across the path of reciprocation of the sewing machine needle when said thread guiding device is secured on said bobbin case.

3. An overedge chainstitch forming attachment as set forth in claim 2 in which said throat plate opening through which said thread guiding finger projects is bordered adjacent to the' needle accommodating aperture with a thread camming edge which traverses beneath the free extremity of the thread guiding finger and serves to position needle thread loops on the free extremity of said thread guiding finger for needle penetration during a subse ue nt needle reciprocation.

4. An overedge c amstrtch forming attachment as set forth in claim 2 in which a projection is formed laterally on the free end of said thread guiding finger, said lateral projection facing away from the needle path of reciprocation and serving to detain needle thread loops thereon until a fresh needle thread loop carried therethrough during a succeeding needle reciprocation deflects the needle thread loop detained on the thread guiding finger.

5. An overedge chainstitch forming attachment as set forth in claim I in which said thread guiding device includes a base portion insertable in the sewing machine loop taker bobbin case in place of a conventional bobbin therein and in which said thread guiding finger is secured to said base portion.

6. In combination with a lockstitch sewing machine having a thread carrying needle reciprocable through a needle aperture in a work support in cooperation with a circularly moving loop taker arranged beneath the work support, mechanism for forming overedge chainstitches comprising an aperture formed in said work support laterally opposite and in communication with said needle bar, a thread guiding device constrained in a stationary position on said loop taker and adapted to influence each loop of needle thread manipulated by said loop taker, said thread guiding device including a thread guiding finger projecting upwardly from said loop taker through said work support aperture to direct each loop of needle thread being manipulated by said loop taker across the edge of a work fabric on said work support.

7. The combination as set forth in. claim 6 in which said thread guiding finger is formed with a free extremity extending across the path of reciprocation of the sewing machine needle. 

1. An overedge chainstitch forming attachment for use on a lockstitch sewing machine of the type having a thread carrying needle reciprocable through a needle aperture in a work supporting throaT plate in cooperation with a circularly moving loop taker which is arranged beneath the throat plate and includes a bobbin case restrained stationary therein, said overedge chainstitch forming attachment including a throat plate formed with an opening laterally opposite the needle aperture therein, a thread guiding device adapted to be secured in a stationary position on said bobbin case so as to be encompassed by each needle thread loop which is manipulated by said loop taker, and a thread guiding finger projecting from said thread guiding device upwardly through said throat plate opening when said thread guiding device is secured on said bobbin case successively to direct each needle thread loop being manipulated by said loop taker upwardly across the edge of a work fabric on the throat plate.
 2. An overedge chainstitch forming attachment as set forth in claim 1 in which said thread guiding finger is formed with a free extremity extending across the path of reciprocation of the sewing machine needle when said thread guiding device is secured on said bobbin case.
 3. An overedge chainstitch forming attachment as set forth in claim 2 in which said throat plate opening through which said thread guiding finger projects is bordered adjacent to the needle accommodating aperture with a thread camming edge which traverses beneath the free extremity of the thread guiding finger and serves to position needle thread loops on the free extremity of said thread guiding finger for needle penetration during a subsequent needle reciprocation.
 4. An overedge chainstitch forming attachment as set forth in claim 2 in which a projection is formed laterally on the free end of said thread guiding finger, said lateral projection facing away from the needle path of reciprocation and serving to detain needle thread loops thereon until a fresh needle thread loop carried therethrough during a succeeding needle reciprocation deflects the needle thread loop detained on the thread guiding finger.
 5. An overedge chainstitch forming attachment as set forth in claim 1 in which said thread guiding device includes a base portion insertable in the sewing machine loop taker bobbin case in place of a conventional bobbin therein and in which said thread guiding finger is secured to said base portion.
 6. In combination with a lockstitch sewing machine having a thread carrying needle reciprocable through a needle aperture in a work support in cooperation with a circularly moving loop taker arranged beneath the work support, mechanism for forming overedge chainstitches comprising an aperture formed in said work support laterally opposite and in communication with said needle bar, a thread guiding device constrained in a stationary position on said loop taker and adapted to influence each loop of needle thread manipulated by said loop taker, said thread guiding device including a thread guiding finger projecting upwardly from said loop taker through said work support aperture to direct each loop of needle thread being manipulated by said loop taker across the edge of a work fabric on said work support.
 7. The combination as set forth in claim 6 in which said thread guiding finger is formed with a free extremity extending across the path of reciprocation of the sewing machine needle. 